auth		required	pam_env.so 
auth		required	pam_unix.so try_first_pass likeauth  
auth		optional	pam_permit.so
account		required	pam_unix.so 
account		optional	pam_permit.so
password	required	pam_unix.so try_first_pass   sha512 shadow 
password	optional	pam_permit.so
session		required	pam_limits.so 
session		required	pam_env.so 
session		required	pam_unix.so 
session		optional	pam_permit.so
